Refrigeration process

ABSTRACT

A REFRIGERATION PROCESS COMPRISES EVAPORATING A REFRIGRERANT FROM AN ABSORBENT SATURATED WITH THE REGRIGERANT BY DIRECT CONTACT WITH A HEAT CARRIER WHICH IS READILY SEPARABLE FROM THE ABSORBER AND REFRIGERANT, THEREAFTER CONDENSING THE VAPORIZED REFRIGERANT BY HEAT EXCHANGE   WITH A COLD CARRIER, THEN EVAPORATING THE REFRIGERANT CONDENSATE BY HEAT EXCHANGE WITH A MEDIUM TO BE COOLED WHICH IS READILY SEPARABLE FROM THE REFRIGERANT AND THEN SATURATING THE COOLED ABSORBENT WITH THE REFRIGERANT VAPORS AND RETURNING THE SATURATED ABSORBENT TO THE INTITIAL EVAPORATION STAGE.

Feb. 23, 1971 'E ETAL Re. 27,074

REFRIGERATION PROCESS.

Original Filed Aug. 19, 1964 I l +J l "ABSORBENT wml I REFRIGERANTCARRIER 1 6 I BOILER comma COLUMN TOWER I I a F- I l L J i 5 UnitedStates Patent Oflice Reissued Feb. 23, 1971 27,074 REFRIGERATION PROCESSMikhail Emmanuilovich Aerov, Tatiana Alexandrovna Bystrova, NinaIvanovna Zeleutsova, and Vera Afauasjevna Kulikova, Moscow, U.S.S.R., byNauchno: Issledovateljsky Institute Sinteticheskikh Spirtov lOrganicheskikh Produktov, assignee, Moscow, U.S.S.R. Original No.3,312,078, dated Apr. 4, 1967, Ser. No. 390,672, Aug. 19, 1964.Application for reissue Aug. 20, 1969, Ser. No. 855,434

Int. Cl. F25b 15/04 US. Cl. 62-112 7 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OFTHE DISCLOSURE A refrigeration process comprises evaporatinga refrigerant from an absorbent saturated with the refrigerant by directcontact with a heat carrier which is readily separable from theabsorbent and refrigerant, thereafter condensing the vaporizedrefrigerant by heat exchange with a cold carrier, then evaporating therefrigerant condensate by heat exchange with a medium to be cooled whichis readily separable from the refrigerant and then saturating the cooledabsorbent with the refrigerant vapors and returning the saturatedabsorbent to the initial evaporation stage.

DESCRIPTION OF THE INVENTION The present invention relates to arefrigeration process for processing moderately low temperatures (+10 to40 C.) in absorption cooling plants.

The known method of producing moderately low temperatures in absorptioncooling plants is based on the use of ammonia and water. According tothis method the heat exchange between the refrigerant, heat carrier andabsorbent is performed through the walls of heat exchange apparatus,that is a boiler, condenser, evaporator, and absorbent cooler which havea large heat exchange surface. Since the difference of temperature ofthe refrigerant and heat carrier varies from 5 to C., a heat carrier ofa higher potential is required. Moreover, the use of a heat exchangedevice with a large heat exchange surface considerably increasesexpenses and does not permit the utilization of low potential waste heatas a heat carrier, e.g., the heat of hot water or low pressure steam.

An object of the present invention is to provide a cooling method inabsorption cooling plants which enables the production of moderately lowtemperatures by the utilization of low potential waste heat, e.g. theheat of hot water or low pressure steam.

Another object of the invention is to provide a refrigeration method inwhich direct heat exchange contact is effected between the refrigerant,the heat carrier and the absorbent.

The above and other objects are attained in a refrigeration process inwhich an absorbent saturated with refrigerant is passed in direct heatexchange contact in a boiler with a heat carrier while heat exchangebetween the heat exchanging media is carried out by direct contact.

The absorbent is constituted by a liquid heavy parafiin hydrocarbonhaving 6 to 10 carbon atoms per molecule. The refrigerant is constitutedby a light paraffin such as ethane, propane and butane. The heat carrieris constituted by waste water or low-pressure steam. In the process, therefrigerant is vaporized in the boiler and escapes from the boiler andpasses into a conljdenser, where it is condensed by contact with a]denser, where it is condensed by contact with a cold carrier, e.g.,water. The thus condensed refrigerant passes [into an evaporator, 'wherei it evaporates [in direct contact] into an evaporator, where itevaporates in' direct contact with the medium to be cooled. Therefrigerant vapors then pass into an absorber, where they saturateabsorbent from the boiler which has been cooled. The thus saturatedabsorbent is then returned to the boiler to complete the process.

The described process may comprise one or more of the aforementionedstages each stage including such steps as boiling, condensing,evaporating, absorbing and absorbent cooling steps. All of said stagescarry out direct contact between the heat exchanging media at least inthe above-mentioned stage of evaporation of the refrigerant in theboiler. The medium to be cooled may be slightly soluble in the[afrementioned] aforementioned hydrocarbons, but must be readilyseparable therefrom. The same is true of the cold carrier. The medium tobe cooled may for example, be water or an aqueous solution of calciumchloride (brine). The hydrocarbons which are dissolved in the coldcarrier are removed by blowing through with a gas which may be slightlysoluble in the cold carrier, e.g. a methane-hydrogen fraction.

The direct contact between the refrigerant, the absorbent, the heatcarrier and cold carrier, enables maintaining temperature differences aslow as 1 to 3 C., which permits the use of hot water as a heat carrierand the utilization of low pressure steam more effectively. Moreover,the direct contact permits the use of simple vessels instead of heatexchangers, thus reducing the expense and the power requirements ofrefrigeration.

The nature of the invention will appear more clearly from the appendedflow diagram illustrating a contact type heat-exchange apparatus[:]comprising boiler 1, condenser 2, evaporator 3, absorber 4, absorbentcooler 5, column 6, cooling tower 7, low pressure pump 8, high pressurepumps 9, 10, and 11, and throttle valves 12 and 13.

According to the method of the invention, refrigeration is produced inthe following way.

The absorbent saturated with refrigerant is delivered into the boiler 1by the pump 11, the heat carrier (hot water or low pressure steam) isalso delivered into the same boiled by the pump 9. In the boiler 1 therefrigerant is vaporized from the absorbent by the heat exchange withthe heat carrier. Heat exchange is efleeted by direct contact betweenthe heat carrier, refrigerant and absorbent in boiler 1. The refrigerantvapors escaping from the boiler 1 are condensed in condenser 2 by directcontact with the cooling water supplied from the cooling tower 7 by thepump 8. The refrigerant condensate formed in the condenser is throttledthrough the throttle valve 12 and is then directed either to the pointwhere it is being consumed, or to the contact-type evaporator 3 where itevaporates in direct contact with the medium to be cooled, thus coolingthe latter.

The heated absorbent flows from the boiler 1 to the absorbent cooler 5where it is cooled by coming into direct contact with water deliveredfrom the cooling tower 7. Then the cooled absorbent and the refrigerantvapors from evaporator 3 are supplied to the absorber 4, the cooledabsorbent having passed through the throttle valve 13. The heat ofabsorption in the absorber 4 is removed by the cooling water in directcontact with the hydrocarbons. Then the saturated absorbent istransferred from the absorber 3 to the boiler 1 and the whole cycle isrepeated.

When butane vapors are used for cooling water, bydrates may form;however, it has been found by experionce that they do not clog theapparatus. Propane hydrates can be decomposed in the presence ofelectrolytic aqueous solutions which are supplied in this case as a.

[refrigerant] medium to be cooled to the evaporator 3 withsmall amountsdelivered at the same'time to the" throttle 12. The cooling water,leaving the condenser 2, absorber 4, and cooler 5, will contain smallamounts of hydrocarbons. In order to avoid the objectionable odor ofthese hydrocarbons (C and up), the water flowing from the condenser 2,absorber 4 and cooler is blown through with the methane or methanehydrogen fraction in column 6.

For the production of brine having a temperature from 20 to 40 C. by theproposed method, a twostage plant is used where a second stage of acondenser, an evaporator, an absorber and [a] an absorbent cooler aresupplied with water or brine already cooled in a first stage.,Theinvention will next be described in conjunction with the followingspecific examples.

EXAMPLE 1 This example is directed to the production of cold water witha temperature of +5 C. using the heat of hot water at a temperature of+90 C.

The refrigerant is butane. The high-boiling absorbent [component] is amixture of parafiins which contains 7 to 8 carbon atoms per molecule.Pressure in the boiler is 4.5 kg./sq. cm., in the condenser 24.5 kg./sq.cm., in the evaporator 3 and absorber 4-1.3 kg./ sq. cm., in the [coler]cooler 54.5 kg./sq. cm. The temperature of the water leaving the coolingtower 7 is C., of the water supplied to the boiler 1 is +90 C., of therefrigerant condensate at throttle 12 is +4 C., of the water beforeentering column 6 is C., and of the cooled water at the outlet of theapparatus is +5 C.

The minimum temperature differences are 12 C., condensation pressure is4.5 kg./ sq. cm., evaporation pressure is 1.3 kg./sq. cm. Butaneconcentration in mole percent is as follows: in the absorbent dischargedfrom the boiler-%, in saturated absorbent-50%, and in refrigerant99%EXAMPLE 2 This example is directed to the production of brine at atemperature of 30 C, in the two-stage plant using the heat of hot waterat a temperature of +90 C The refrigerant is propane. The absorbentcorresponds to that in Example 1. The assembly of elements 2, 3, 4 and 5is supplied with brine having a temperature of +5 C., said brine havingbeen obtained in a first stage by using butane as the refrigerant,according to Example 1.

In the second stage the condensation pressure is 6.5 kg./sq. cm., theevaporation pressure is 2 kg./sq. cm., propane [condensation]concentration in mole percent in absorbent discharged from the boiler inthe second stage is 22%, in the saturated absorbent34%, in therefrigcram-100%.

What is claimed is:

1. A method of effecting refrigeration in absorption tcoioling' plantscomprising evaporating a refrigerant from an absorbent saturated withsaid refrigerant by heat exchange with a heat carrier which is readilyseparable from said absorbent and refrigerant, said refrigerant being alight parafiin hydrocarbon, said absorbent being a liquid, 5 heavyparafiin hydrocarbon, condensing the vaporized refrigerant by heatexchange with water'as a cold carrier, evaporating the refrigerantcondensate by heat exchange with a medium to be cooled which is readilyseparable from the refrigerant, saturating cooled absorbent with therefrigerant vapors and returning the saturated absorbent to the initialevaporation stage, the steps of the heat exchange between saidabsorbent, said heat carrier, said cold' carrier, and said refrigerantbeing carried out by direct contact.

2. A method as claimed in claim 1 wherein said heat carrier is hotwater.

3. A method as claimed in claim 2, wherein said heat carrier is lowpressure steam.

4. A method as claimed in claim 1 comprising blowing through the waterserving as a cold carrier [through] a gas which is not soluble in thecold carrier to remove any dissolved hydrocarbons.

5. A method of effecting refrigeration in an absorption cooling plantcomprising evaporating a refrigerant from an absorbent saturated withsaid refrigerant by heat exchange with a heat carrier which is readilyseparable from said absorbent and refrigerant, said refrigerant being alight paraffin hydrocarbon the absorbent being a liquid, heavy paraffinhydrocarbon; condensing the vaporized re- 30 frigerant by heat exchangewith cooling water constituting a cold carrier, evaporating therefrigerant condensate by heat exchange with the medium to be cooled;cooling the absorbent after the heat exchange with the heat carrier;saturating the thus cooled absorbent with vaporized re- 35 frigerantproduced after contact with the medium to be cooled and recirculatingthe thus saturated absorbent to the initial stage of evaporation wherebya continuous process is obtained, said steps of heat exchange betweensaid absorbent, said heat carrier, said cold carrier and 40 saidrefrigerant being carried out by direct contact at least at theabove-mentioned initial stag of evaporation. 6. A method as claimed inclaim 5, wherein said heat carrier is hot water.

7. A method as claimed in claim 5, wherein said heat carrier is lowpressure steam.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,041,741 5/1936 Bichowsky 621l2 2,045,204 6/1936Shagoloff 62102 2,290,506 7/1942 Thomas 62-402 2,667,764 2/1954 Turner62-101 WILLIAM E. WAYNER, Primary Examiner

